Catalytic apparatus



ATTORN EYs l /NvEA/rok E. v MATHY E. V. MATHY CATALYTIC APPARATUS FiledSept. 19, 1946 Dec. 26, 1950 Patented Dec. 26, 1950 CATALYTIC APPARATUSEugene V. Mathy, Bartlesville, Okla., assignor to Phillips PetroleumCompany, a corporation Delaware Application September 19, 1946, SerialNo. 697,964

1 Claim. 1

This invention relates to the endothermic catalytic conversion ofhydrocarbons. Certain aspects of the invention relate to novel catalyticapparatus. The invention in one embodiment relates to the catalyticcracking of hydrocarbons to form lower boiling hydrocarbons in thepresence of added diluent gases. This invention further relates tcatalytic conversions of the nature described in which catalystregeneration is eiected by introduction of regeneration gas at aplurality of points in a reactor containing one or more stationary bedsof catalyst.

The catalytic conversion of hydrocarbons has become of great commercialimportance. It has frequently been found desirable to effect thereaction in the presence of added gases which may act as diluents cr asreactants. These gases frequently are added at one or more intermediatepoints along the line of flow of the reaction mixture, the object beingeither to supply heat or cooling to the reaction or to provide bettercontrol of reactant concentration. Furthermore, in some instances it isdesired to change the character of conversion at a mid-point byeffecting a substantial change in reaction mixture composition,temperature, or flow rate.

In adding gases of the nature described it has been customary tointroduce same by means of spreaders located Within the catalyst chamberand comprising multiple radial arms of pierced conduits of one type oranother. Only imperiect distribution and mixing are thus obtained, andsome of the openings frequently become plugged thus further lesseningthe eiciency and uniformity of distribution of the incoming gases. Inorder to minimize these undesirable eiects the catalyst is sometimesemployed in the form of a plurality of beds separated by void spaces ofconsiderable size. The spreaders are located Within these catalyst-freespaces, thus allowing a substantial time for intermixture to occur priorto bringing the reaction mixture again into contact with the catalyst.This arrangement, however, is frequently undesirable particularly in thecase of catalytic cracking of hydrocarbons, in that catalytic reactionscease and thermal reactions are allowed to proceed in the void spaces.This results in the production of products of an entirely differentnature from those resulting from the action of the catalyst, Withconsequent inefciencies of product distribution and diiiiculties insubsequent product separation steps.

Another problem arising in fixed-bed catalytic hydrocarbon conversionsis the so-called Wall effect. This term derives its name from the.2s-ass) fact that gas flow is more rapid toward the periphery of acatalyst chamber then in the center. This results in uneven use of thecatalyst and in very substantial temperature differentials' betweencenter and edge of the catalyst bed;

The more rapid ow along the Walls also encourages the formation ofchannels through the catalyst bed with consequent unevenness of flow.

It is an object of this invention to provide anV Yet another object isto improve the rapidityand uniformity of mixing of such added gases. Afurther object of the invention is to provide improved catalyticapparatus.

An additional object is to crack hydrocarbonscatalytically in thepresence of steam.

A further object of the invention is to improve the regeneration ofspent hydrocarbonconverv sion catalysts.

Other objects and advantages of the invention Will be apparent to oneskilled in the artl from the accompanying disclosure and discussion. x

'I'he present invention will be described with particular reference tothe cracking of gas oili or the like over a cracking catalyst in thepresence of steam. It will be understood that the principles of theinvention may readily be ap-V plied to other conversions with suitablemodication Where necessary. In accordance with a.

preferred embodiment of the invention, a cylindrical catalyst chamber isseparated into two or more sections by means oi a streamlined annularstructure projecting from the inside surface of the catalyst chambertoward the center thereof,` in a manner shown in detail in theaccompanying drawing. Within this annular structure is located anannular conduit for carrying diluent or reactive gases, which areintroduced into the. catalyst chamber by means of a plurality of in letnozzles or jets directed toward the center of the chamber. free ofcatalyst at this point to allow rapid and intimate mixture of gases. Theannular divid- A verysmall space is maintained ing structure isstreamlined on the upper and lower surfaces so that gases flowing alongthe chamber wall are caused to converge toward the axis of the chamberin streamlined liow, and after admixture of reactant gases with thegases introduced by means of the inlets described above the gasesleaving the mixing zone continue their flow through the catalyst chamberin a stream@ lined manner so that the gas mixture near the wallsgradually flows outwardly toward the cy lindrical portion of the wall inthe latter part of the catalyst chamber. One or more annular inletstructures of the nature described may be ernployed in a given catalystcase, Vin accordance with the particular conversion being effected.

In the present description and claims, streamlined flow and iiow in astreamlined manner means unbroken nonturbulent flow of fluids over asurface and past a body. Streamlined construction means a surface whichproduces such smooth nonturbulent flow and over which nuids will pass inunbroken nonturbulent manner. Such streamlined surfaces are, ofnecessity, smooth and regular divergent o1' convergent curvatures.

By streamlined construction and ow of gases in the catalyst chamber, acentral restricted point of high turbulence is set up into which areinjected the diluent or reactive added gases. An

extremely rapid and intimate mixing is thus ob" :u

tained. The flow of gases, however, is then rap idly restored tosubstantially non-turbulent .flow through the catalyst by means of thestream lined construction of the lower surface of the inlet structure.bed are themselves curved in shape at their lower and upper extremities,respectively, and the flow of gases therethrough is made much moreuniform than would be the case if they were purely cylindrical. Voidspace within the catalyst chamber is reduced to a minimum by my `methodof construction and operation. Prefm erably the upper part of thecatalyst chamber is also streamlined so that the top of the uppercatalyst bed is shaped similarly to the top of the lower catalyst bed.Likewise, the lowest portion of the chamber wall may be shaped similarlyto the streamlined upper surface of the annular inlet structure.

Preferably the annular inlet structure of the invention is fabricatedfrom an insulating cement rather than from metal, with resultant economyof manufacture, operation, and upkeep, since it has been found thatmetal used at this point is subject to rather severe corrosion anderosion. Accordingly, the use of expensive alloy steels is reduced to aminimum.

The accompanying drawing shows in somewhat idealized form one preferredform of apparatus suitable for the practice of my invention. It will beappreciated that certain modications may be made without departing fromthe scope and spirit of the invention.

In the drawing, the reaction chamber comprises a vertical cylinder Ihaving a concave top II and concave bottom l2. A large inlet conduit I3is provided at `the top axially located with respect to the cylinder andhaving a flange I4 for connection to the transfer line (not shown) bymeans of which reactants are passed l into the reactor. Cup-shaped bale2l! (supported by means not shown) aids in initial distribution ofreactants. Screen 2| may be placed on top of the top catalyst bed IB.After iiow through the chamber the reaction mixture exits The upper andlower catalyst I- Ell through a centrally located outlet conduit I5provided with a flange I6 for connection with a transfer line (notshown) which is used to pass reaction products to separation andfractionation steps. The outside shell of chamber I, including the topII and bottom I2, is made of metal having sufficient strength to supportthe material inside and capable of withstanding the conditions ofoperation. Preferably this is constructed of steel having a thickness ofabout 1 inch. The shell is provided with an internal insulating liner 2which may be about 6 to 12 inches in thickness, depending upon theamount of insulation required.

The liner is cast within the shell from an insulating refractory cementas from a suitable commercial product such as Insulcrete, "Panelag, orthe like. The liner is fastened to the shell by any of a number of wellknown means (not shown) and may also include reinforcing metal, vaporstops, or other known elements for reinforcing the insulation and formaking the liner impervious to the now of vapors.

At one or more levels in the reactor where it is desired to inject thediluent gases, an annular constricting element 4 built up of castinsulation is installed. This construction is made in the form shown sothat the flow of gases over its outer surface is always streamlined. Itis composed of insulating cement similar to that used in casting liner2. Reinforcing bars 5 which are fastened to the outer shell I of thevessel are used to support the casting. Element 4 is of such size thatthe open iiow area at the cen ter of the catalyst chamber is preferablyfrom 25 to 40 per cent of the maximum cross-sectional area of thechamber. A conduit means B for admitting the gases to the distributor l0is embedded in the insulation. The distributor i0 is a circular annularconduit embedded just inside the inner wall of the constriction Il. Thisdistributor has a multiplicity of extended openings 9 in the form ofnipples, nozzles or iets which connect with the space 22 within theconstricf tion. This space 22 is enclosed on both the top and the bottomby supported screens 6 and I'I, respectively, which are strong enough tosupport the weight of the catalyst above and yet are fine enough t0prevent passage of catalyst particles. The screens may be made up from agrid of 1A" x l bars on edge with openings l to 11/2" wide on top ofwhich is laid a li-rnesh screen which in turn is covered by a ISO-meshscreen. The space 22 enclosed by these screens and into which thediluent gases are injected is quite small with respect to the totalcatalyst volume, yet provides sufficient space for the rapid andintimate mixing of the'gases 0r vapors which are injected through theconduit 8 and the reactants passing through this space 22 from thecatalyst bed above. The upper portion of the chamber contains catalystbed I 8 resting on screen is". It will be noted that this bed is notwholly cylindrical but that the diameter of the lower portion thereofgradually and smoothly decreases so that gases owing through the bednear its periphery approach the center of the catalyst chamber instreamlined manner. Furthermore, the upper portion of bed I 8 likewisedeviates from the cylindrical in streamlined manner as shown. The lowersection of the catalyst chamber contains catalyst bed I9 which rests onthe supporting screen box 1 and which extends completely up to screen Il, which is the lower boundary of the inlet space 22 defined by screensI 'l and 6. It will likewise be noted that catalyst bed I9 iscylindrical in the lower portion thereof but that the diameter of theupper portion gradually and regularly decreases as the top of the bed isapproached, thus insuring streamlined ow of gases as explained. Thelower portion of bed I9 may also be constricted into a shape similar tothat of the lower portion of bed I8 in order to minimize the walleffect,although this is not shown in the particular embodiment illustrated inthe drawing.

In a straight-walled chamber the gases travel through the portion of thecatalyst bed near the walls at a faster rate than in the center of thebed. By virtue of the venturi construction shown herein, the rate offlow is substantially equalized. In other words, the time required forflow from top to bottom of catalyst beds is substantially equal for allportions of the gas passing therethrough. In eontradistinction to theconventional spreaders which result in uneven distribution, the highturbulence within the space 22 defined by screens 6 and I? caused by thestreamlined construction and by the jets 0 entirely eliminates thisproblem. A partial plugging of jets 9 does not substantially reduce theeiciency of mixing, Whereas, any plugging in the conventional drum-typespreader causes mal-distribution.

In order to illustrate certain features of the invention the followingexample is given. It will, of course be understood that otherconversions may be effected in accordance with the invention, and thatvarious changes may be made in proportions, catalyst, and reactionconditions without departing from the broad scope of the invention.

In a typical gas oil cracking run using a vertical cylindrical catalystchamber with drum spreaders placed at the mid point of the chamber, 190barrels per hour of oil at a space velocity of one liquid volume oil pervolume of catalyst per hour and 9,000 pounds of steam per hour werecharged to the top of the catalyst chamber. A bauxite catalyst of about8-14 mesh was employed. The inlet vapors entered the catalyst at 1020cF. and at 85 p. s. i. pressure. Steam at 1100 F. was injected into thespreader connection of the chamber at the rate of 2800 pounds per hour.

During operation of this chamber the temperature profile when taken in ahorizontal plane across the bed showed temperatures at the edge of thebed as much as 40 F. higher than those at the center. In contrast, whenoperating under the same conditions with a chamber constructed inaccordance with the present invention as described above, much betterdistribution of the injected steam is obtained. I'he temperaturegradient between the walls and the center of the reactor is greatlyreduced and the maximum gradient ranges from about l0 to 15 F.

In the regeneration of the catalyst masses after completion of theprocess cycle, by burning carbonaceous matter from the catalyst by meansof air and steam, a burning Zone passes from the top to the bottom ofthe catalyst bed. This burning zone in the wholly cylindrical chamberhas a front in the shape of an inverted saucer. However, when thechamber is constructed in accordance with the principles describedherein the burning zone when in the upper portion of the chamber isleveled out due to the shape of the catalyst bed. The gases are thenthoroughly mixed with added combustion gases in the mixing space andthen redistributed so that the burning zone is also leveled out when inthe lower chamber. In a vertical catalyst chamber an important saving inregeneration is obtained by keeping the burning zone level andhorizontal, in that regeneration gases are not wasted by prematurebreakthrough near the chamber walls.

I claim:

An improved catalytic reactor adapted for endothermic catalyticreactions wherein diluent or reactant gases are introduced into thereaction mixture at an intermediate point, which comprises an elongatedvertical cylindrical catalystcontaining chamber internally insulatedwith refractory cement and having an axial inlet and axial outlet atopposite ends thereof, a catalystretaining transverse screen within saidchamber near the outlet thereof, and at least one annular structure asdescribed hereinbelow intermediate the inlet and said screen dividingsaid chamber into at least two sections, each said section having acentral cylindrical portion, said annular structure having concave topand bottom surfaces of refractory insulating cement each tangentiallyjoining said central cylindrical portions of their respective sectionsand regularly converging inwardly and toward each other in smoothunbroken arcuate curves toward but not attaining the horizontal to forma restriction to the flow of fluids passing through said chamber, theinner diameter of said annular structure being such that the restrictedopening between the sections has a cross-sectional area of from 25 to 40per cent that of the cross-sectional area of the cylindrical portions ofsaid sections, a pair of parallel transverse catalyst-retaining screensextending across and adjacent said restriction and together with theinner surface of said annular structure defining a catalyst-free spacequite small with respect to the total catalyst volume, the uppermost ofsaid pair of screens plus the upper curved surface of said annularstructure being adapted to support a bed of catalyst thereupon wherebysaid bed of catalyst will have a smoothly curved lower surfacecorresponding to said upper annular surface, the lowermost of said pairof screens plus the lower curved surface of said annular structure beingadapted to confine a bed of catalyst filling the section of chambertherebelow whereby said bed of catalyst will have a smoothly curvedupper surface corresponding to said lower annular surface, an annularconduit within each said annular structure, means for supplying fluid tosaid conduit, and a plurality of inlets extending from said conduit intosaid space for iiow of fluid thereinto for admixture with iluids passinglongitudinally through said chamber.

EUGENE V. MATI-IY.

REFERENCES CITED The following references are of record in the ile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,144,730 Schaefer June 29, 19151,959,898 Brode et al -I May 22, 1934 2,353,509 Schulze et al. July 11,1944 2,417,348 Carter Mar. 11, 1947

